Process for producing de-waxed citrus oils



United States Patent 3,155,648 PRUCESS FOR PRUDUQENG DE-WAXED QETRUS GILS Horton E. Swisher, Upland, Calif assiguor to Sunkist Growers, inc, Los Angeles, Calif., a corporation of Qalifornia No Drawing. Filed Apr. 3, 1961, Ser. No. 100,016 14 Claims. (Cl. Mil-236.6)

This invention relates to the treatment of citrus products and has particular reference to a process for the production of de-waxed citrus oils and other essential oils.

Wax-free citrus oil, particularly cold pressed lemon oil, is in great demand, the purchasers of lemon oil requiring that it meet with U.S.P. requirements, one requirement being that the oil shall produce a clear alcoholic extract. In recent years the problem of removal of was and waxlike materials from citrus oils has become increasingly difficult and it has become virtually impossible to produce USP. lemon oil, due in part at least to the changes that have taken place in the waxing of citrus fruits. Because of the need for fruit-waxing compositions that have high gloss and effectively prevent shrinkage of the fruit on storage, new and better wax compositions are constantly being formulated. Among the materials that are being introduced into these wax compositions are carnauba wax, paraflin wax, limed polypale resin, polymerized terpenes and coumarone-indene resins.

Some of these newer wax additives, such as coumaroneindene resin, are so highly soluble in citrus oils and so chemically unreactive that heretofore there has been no known way to remove them without altering the composition of the oil. Naturally occurring waxes or stearoptenes can be effectively removed by low temperature filtration of the oil using means known in the art, but such materials Patented Nov. 3, 1964 Another object of the present invention is to provide a process for de-waxing citrus oils without affecting the composition of the oil, other than the removal of the wax therefrom.

Still another object of the present invention is to provide an improved process for the extraction of a substantially wax-free oil from the peel of citrus fruit.

Other objects and advantages of the present invention it is believed will be readily apparent from the following detailed description of preferred embodiments thereof.

Briefly, this invention comprehends within its scope the discovery that synthetic and natural waxes and wax-like materials present in essential oils such as citrus oils are precipitated by the addition to the oil of an oil-soluble fluorochlorohydrocarbon. Such compounds have been found to be ideally suited as de-waxing solvents for such difiicultly removed compounds as coumarone-indene resin and in addition, these de-solvents also easily remove other wax additives as well as the naturally occurring stearoptenes of the citrus oils. Further, it has been found possible to control the amount of wax removal by regulating the quantity of de-solvent. It has further been discovered that in addition to utilizing these compounds as by addition to the pressed oil, the compounds can be used to extract the oil from the peel and simultaneously bring about the separation of the wax from the oil.

The process of the present invention is particularly adapted to the de-waxing of such citrus oils as lemon, lime, orange, grapefruit and tangerine, but other terpene-containing essential oil, such as those of the mint group can also be treated in accordance with the present invention.

The fluorochloromethanes and ethanes have been found to be particularly suitable for use in the process of the present invention. A list of compounds useful within the scope of the present invention is set forth in Table I.

TABLE 1 Physical Pr perties of Fluorocarbon Compounds Heat of Specific 33.1. at Density of vaporiheat of Viscosity Chemical name Formula 1 atm., liquid at zation liquid at of liquid C. 30 C. at B.P 30 0., at 30 0.,

B .t.u./lb B .t uF/1bJ eentipoise Trichloromonoflnoromethane (C 0131 23. 8 1. 464 78. 3 0. 209 0. 405 Dichlorodifluoromethane 29. 8 1. 292 71. 0 O. 240 O. 251 Dichloromonofluoromethane 8. 9 1. 354 104. 2 0. 256 0. 330 Monochlorodifluoromethane 40. 8 1. 175 100. 7 0. 335 0. 229 Trichlorotrifluoroethane 47. 6 1. 553 63. 1 0. 218 0. 619 Dichlorotetrafluoroetbane (C ClF2-C OlF 3. 6 1. 440 59. 0 O. 238 0. 356 Octar'luorocyclobutane (CF2CFzCFzCF2) 6. 0 1 1. 513 1 46 1 0. 26 1 0. 455

as coumarone-indene resin have sufiicient solubility in lemon oil to remain in solution even when the oil is chilled and filtered at 78 C. Since citrus fruits that are received by the oil processing plants are largely those that have been waxed in the packing house, they contain varying amounts of both the naturally occurring and synthetic waxes. In pressing the citrus oil from the peel, it is virtually impossible to prevent contact of the oil and surface wax and as a consequence, a considerable amount of the natural and added surface wax becomes dissolved in the oil during the pressing operation.

A primary object of the present invention is therefore to provide a process for the removal of synthetic and natural waxes and wax-like material from citrus oils and other essential oils.

A further object of the present invention is to provide a process for the production of lemon oil meeting the requirements of the U.S.P.

All of the straight chain fluorochlorohydrocarbons listed listed in Table I are miscible with citrus oils. The cyclic compound, octafluorocyclobutane, however, has ,been found to be immiscible with the oils. It is useful as a desolvent in the process of the present invention only when it is used in combination with the other compounds in amounts low enough to be miscible with these oils. In addition to the wholly chlorofluorinated hydrocarbons set forth, partially iluorinated hydrocarbons that are oil-miscible such as dichloromonofluoromethane and monochlorodifluoromethane can be used, either alone or in combination with the wholly chlorofluorinated hydrocarbons, which of course can also be used in mixtures of two or more.

In carrying out the process of the present invention, as applied to the de-waxing of an extracted oil, the de-solvent is simply mixed, in the liquid state, with the oil and the mixture allowed to stand for a sufficient length of time to precipitate the wax. The wax is removed from the oil and de-solvent mixture by any convenient method such as filtration, and the oil is recovered by vaporizing the desolvent therefrom.

top of the glass vessel within 5 minutes to form a heavy flocculant precipitate which occupied 6.8% of the total volume of the mixture. The mixture was filtered rapidly at C. through paper and the tie-solvent separated from An alternate method comprises the use of the de-solvent the oil by heating to 50 C. under a partial vacuum. as an extractive solvent for the peel oil. That is, the de- The de-waxed oil prepared in the above manner gave a solvent is mixed, for example, with citrus peel flavedo, the sparkling alcoholic extract whereas the untreated oil conde-solvent preferentially dissolving or extracting the citrus tained at large amount of flocculant precipitate. When oil without bringing the wax into solution. The de-solvent both the treated and untreated oils were examined by is removed from the oil in the same manner as above, methods of gas phase chromatography at temperatures of to produce the de-Waxed citrus oil product. 65 C., 100 C. and 150 C., no discernible differences in The following specific examples are illustrative of the either composition or traces of residual solvent were process of the present invention, but it is to be understood noted. The de-waxed oil had a normal evaporation resithat the invention is not to be limited to the specific dedue of 2.32%. ails thereof. EXAMPLE 3 For purposes of determining whether the citrus oils produce clear alcoholic extracts the standard test applied one Volume of the Same 9 PIFSSed lemon (mils used t in Example 2 above was mixed with 3 volumes dichloroin each case was as follows. 1 cubic centimeter (cc.) or tetrafluomethme at c in a Fische and Porter hss the citrus Oil was mixed at room temperature in a stopaerosol ress ure bottl ivhereu on 2i wax reci itate pered test tube with 9 cc. of 95% ethyl alcohol and the formed mixture 5 shakenp criodican fhile g mixture observed for formation of cloud. After 24 hours allowe to Warm u SIOWI throw; the tem Zrature ran 5 the mixture was again observed for any precipitate that f p I f a g might have formed rom C. to C. t temperature interva s o 5 C., 7 samples of oil and de-solvent mixture were withdrawn EXAMPLE 1 25 immediately after vigorous shaking, through an aerosol For this test a commercial sample of clarified cold spray nozzle. The fine spray of the nozzle was directed pressed lemon oil which had been unsuccessfully de-waxed into a paper filter where the sudden expansion to atmosby a standard treatment at 40 C. was used. As is indipheric pressure of the mixture caused a temperature drop cated in Table II below, several ratios of de-solvcnts were below the boiling point of dichiorotetrafiuoroethane. The used with this lemon oil to establish the proper amounts tie-waxed lemon oil that passed through the filter paper required to effect suificient de-waxing so as to produce was warmed to remove the residual desolvent and made cloud-free alcoholic extracts. The oil and the dichloroup into alcoholic extracts. All of the oils, which were tetraiiuoroethane were mixed at 10 C. in a Fischer and withdrawn at temperatures of 10 C., 15 C., 20 C. and Porter glass vessel, allowed to stand 15 minutes at -10 25 C., gave clear alcoholic extracts. By way of com- C. and the precipitated wax removed from the lemon oil parison, another mixture was made up in the same mande-solvent mixtures at atmospheric pressure by gravity ner in a glass pressure bottle, but in this case the mixture filtration through paper. was withdrawn at 25 C. from the clear liquid below the Because of the lower boiling points of the dichlorotop wax layer and was not filtered after being released to 'difiuoromethane and monochlorodifiuoromethane they atmospheric pressure. After removing the residual dewere mixed and filtered at 30 C. and 40 C. respec- 40 solvent, this oil produced a very slight haze in the alcoholic tively. extract made therefrom. The untreated control lemon oil The lemon oil was recovered by heating the mixture on produced a large amount of fiocculant precipitate in ala steam bath sufiiciently to vaporize the low-boiling decohol. solvent. The lemon oil thus obtained was tested for Thus, it can be seen that the waxes of the lemon oil cloud in alcoholic solutions as detailed above, with the have a slight solubility in the mixture of oil and de-solvent results indicated in Table II. at 25 C. However, the wax can be effectively removed TABLE II De-waxing Clarified Cold Pressed Lemon Oil De-waxing treatment Alcoholic Extract Parts Test; No. Lemon oil y VOL) Parts De-soivent desolvent Appearance of After 15 min. After 24 hours (by vol.) cloud in mixture Control Slightcloud--- Moderate precipitate. 2 Dichlorotetra- 1 Remained clear do Do.

fluoroethane. 1 o-.. 1 Slightly hazy do Do. 1 2 Small floeculant Very slight Slight precipiprecipitate. cloud. tats. 1 2.5 Flocculant pre- Clear Nopreeipitate.

cipitate. 1 do 3 --do do Do. 1 Diehlorodi- 2.5 Small flocculant Very slight Very slight fluoromethane. precipitate. cloud. precipitate. 1 do 3 Fl occtulantprecip- Clear No precipitate.

1 {I e. 1 Monochlorodi- 3 Smallfiocculant Very slight Very slight iluoromethane. precipitate. cloud. precipitate.

EXAMPLE 2 from the lemon oil even at ambient temperatures by allow- One volume of a commercial sample of cold pressed lemon oil, which had been only partially de-waxed in manufacture, was mixed with 3 volumes dichlorotetrafluoroethane at 0 C. in a glass pressure vessel. A dense cloud of wax formed almost immediately and rose to the ing the de-solvent to provide its own evaporative cooling by expansion, just prior to filtration or centrifugation.

EXAMPLE 4 The de-waxing method described above was repeated with cold pressed grapefruit oil, cold pressed orange oil and concentrated (5-fold) orange oil. One volume of each oil was mixed with 3 volumes dichlorotetrafluoroethane at C. in a pyrex glass bottle, allowed to stand 30 min utes, filtered cold through paper and the de-solvent evaporated. Considerable wax separated fromeach of the oils. When mixed with alcohol as previously described, the grapefruit oil gave a clear extract wherea the control was cloudy. In the case of the cold pressed and concentrated orange oil, the cloud was improved over the controls, but complete clarity was not achieved. It should be pointed out that the U.S.P. specification for cold pressed orange oil requires only that it be miscible with dehydrated alcohol, a test that is less severe than the test applied in this case.

EXAMPLE In another experiment, 3000 ppm. of coumaroneindene resin was added to one sample of clarified lemon oil, 1000 ppm. of limed polypale resin added to another and 1% (by weight) of the soft wax separated from lemon oil in the plant centrifuges added to other. in each case the lemon oil resulting from treatment with 3 volumes of dichlorotetrafluoroethane gave clear alcoholic extract.

in commercially applying this process for de-waxing citrus oils, the de-solvent treatment of the oil is preferably accomplished in a closed system by mixing, removing the coagulated waxes by filtering, centrifuging, etc. After wax removal the tie-solvent is separated from the oil in an evaporator and the oil drawn off. After condensing the de-solvent it is ready for recycling in continued use.

The final traces of de-solvent in the oil may be removed by vacuum treatment and/ or warming as required. Alternatively, purging with nitrogen gas also may be used. If desired the oil may be washed with water to remove any water-soluble or Water-miscible trace components.

The amount of de-solvent required varies, depending upon the type of de-solvent, the type of oil being de-waxed and the wax content thereof. Generally speaking, this ranges from about 1 to 5 volumes of de-solvent for each volume of oil, with from about 2 to about 4 volumes of de-solvent per volume of oil being preferred.

Whereas all the above examples have covered de-waring citrus oils that were made by the usual process in which the unwanted waxes were already present in the cold pressed oils, the following example circumvents this problem by using the de-solvent as an extractive solvent for the peel flavedo. Thus, it is possible to make a lemon oil producing cloud-free alcoholic extracts simply by extracting the peel with a solvent that preferentially dissolves the citrus oil without bringing the wax into solution.

EXAMPLE 6 24 grams of finely grated lemon peel were chilled and mixed with 60 cc. of dichlorotetrafluoroethane at 0 C. in a glass pressure vessel. The mixture was allowed to warm up to room temperature, with occasional shaking, over a period of 3 hours. Following this treatment the mixture was again chilled to 0 C. and filtered through paper to separate the peel and desolvent-oil mixture. After removing the desolvent by warming on a steam bath, the recovered lemon oil was tested for cloud by preparing an alcoholic extract. This extract was sparkling clear.

As will be apparent to those skilled in the art from the above examples, the present method for the removal of waxy constituents from essential oils has certain definite advantages, as follows:

(1) It generally requires only from two to three volumes of de-solvent for each volume oil to be de-waxed, which is a favorable ratio by comparison with other methods.

(2) It does not require extremely low temperatures for efiicient removal of Wax.

(3) Rather than the typical soft slimy wax formed when stearoptenes are formed at low temperatures in oil, the wax that separates in the mixtures of oil and de-solvent tends to be hard and easily removed by filtration or by centrifugation.

(4) The viscosity of the oil and de-solvent mixture is low, even at very low temperatures, making filtration easy.

(5) Because of the resulting high density of the oil and de-solvent mixture, the lighter wax tends to float to the surface, thus facilitating removal.

(6) The low boiling points of the de-solvent compounds makes possible their removal from the oil without having to subject the mixture to relatively high temperatures.

(7) The heat of vaporization of the de-solvents is only a fraction of that of other possible de-solvents. Thus, much less heat energy is required to remove the desolvents of the present invention from the oil than would be required for other known de-solvents.

Having fully described my invention, it is to be understood that I do not wish to be limited to the details set forth, but my invention is of the full scope of the appended claims.

I claim:

1. A process for removing coumarone-indene resin from citrus oil comprising the steps of subjecting a citrus oil which contains coumarone-indene resin to the action of a sufiicient volume of a citrus oil-soluble fluorochlorohydrocarbon is selected from the group consisting of trichloromonofluoromethane, dichlorodifiuoromethane, dichloromonofluoromethane, monochlorodifluoromethane, tri chlorotrifluoroethane, dichlorotetrafluoroethane, and mixtures thereof to precipitate the resin, separating the precipitated resin from the liquid phase and separating the fiuorochlorohydrocarbon from the citrus oil.

2. The process of claim 1, wherein the fluorochlorohydrocarbon is used in an amount between about one and about five volumes for each volume of oil.

3. The process of claim 1 wherein the fluorochlorohydrocarbon is mixed with the oil, wherein the wax precipitate is filtered from the liquid phase, and wherein the fiuorochlorohydrocarbon is separated from the oil by heating the liquid phase to vaporize the fluorochlorohydrocarbon.

4. The process of claim 3 wherein the fluorochlorohydrocarbon comprises from about two to about four volumes of dichlorotetrafiuoroethane for each volume of oil.

5. The process of claim 3 wherein the fluoroch1oro hydrocarbon comprises from about two to about four volumes of dichlorodifluoromethane for each volume of oil.

6. The process of claim 3 wherein the fluorochlorohydrocarbon comprises from about two to about four volumes of monochlorodifluromethane for each volume of oil.

7. The process of claim 1 wherein the fluorochlorohydrocarbon is added to citrus peel to extract the substantially wax-free oil therefrom.

8. The process of claim 1 including the steps of adding the fiuorochlorohydrocarbon to the oil-bearing portions of the citrus peel at a temperature below the boiling point of the fluorochlorohydrocarbon, warming the admixture to room temperature, chilling the admixture to a temperature below the boiling point of said fiuorochlorohydrocarbon, separating the liquids from the solids, and heating the liquids to vaporize the fluorochlorohydrocarbon therefrom.

9. The process of claim 8 wherein the fluorochlorohydrocarbon comprises from about two to about four volumes of dichlorodifiuoromethane for each volume of oil.

10. The process of claim 8 wherein the fluorochlorohydrocarbon comprises from about two to about four volumes of dichlorotetrafluoroethane for each volume of oil.

11. The process of claim 8 wherein the fiuorochlorohydrocarbon comprises from about tWo to about four volumes of monochlorodifluoromethane for each volume of oil.

12. The process of claim 4 wherein the citrus oil is lemon oil.

13. The process of claim 1 wherein said citrus oil comprises a cold pressed citrus oil.

14. The process of claim 1 wherein said oil comprises a cold pressed lemon oil and said fluorochlorohydrocarbon comprises dichlorotetrafiuoroethane.

References Cit-ed in the file of this patent UNITED STATES PATENTS Barnes et a1 May 16, 1939 Rubin Aug. 14, 195] Platt et a1 May 24, 1960 FOREIGN PATENTS France Oct. 12, I959 

1. A PROCESS FOR REMOVING COUMARONE-INDENE RESIN FROM CITRUS OIL COMPRISING THE STEPS OF SUBJECTING A CITRUS OIL WHICH CONTAINS COUMARONE-INDENE RESIN TO THE ACTION OF A SUFFICIENT VOLUME OF A CITRUS OIL-SOLUBLE FLUOROCHLOROHYDROCARBON IS SELECTED FROM THE GROUP CONSISTING OF TRICHLOROMONOFLUOROMETHANE, DICHLORODIFLUOROMETHANE, DICHLOROMONOFLUOROMETHANE, MONOCHLORODIFLUOROMETHANE, TRICHLOROTRIFLUOROETHANE, DICHLOROTETRAFLUOROETHANE, AND MIXTURES THEREOF TO PRECIPITATE THE RESIN, SEPARATING THE PRECIPITATED RESIN FROM THE LIQUID PHASE AND SEPARATING THE FLUOROCHLOROHYDROCARBON FROM THE CITRUS OIL. 